style: apply current rustfmt to the tree

A newer rustfmt wraps over-long match arms and call expressions that the
version main was last formatted with left on one line. Pure formatting,
no semantic change — split out so the friends-list feature commits stay
focused on real changes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/host/pipeline.rs

@@ -308,7 +308,9 @@ async fn default_audio_monitor() -> Result<String> {
         .arg("get-default-sink")
         .output()
         .await
-        .context("failed to run `pactl get-default-sink` (install pulseaudio-utils or pipewire-pulse)")?;
+        .context(
+            "failed to run `pactl get-default-sink` (install pulseaudio-utils or pipewire-pulse)",
+        )?;
     if !output.status.success() {
         bail!(
             "pactl get-default-sink failed: {}",